1. Field of the Invention
The present invention relates to an information recording medium and an editing apparatus therefor, particularly, relates to a rewritable information recording medium which is divided into a plurality of sectors having predetermined volume of data, and relates to an editing apparatus and method of editing audiovisual information recorded in the information recording medium.
2. Description of the Related Art
It is commonly performed that data of digital audiovisual information are compressed and the compressed data are recorded in an information recording medium with recent progress and development of information processing technology. With respect to video information, particularly, a total volume of information content is huge. Therefore a high degree compression technology is utilized for an information recording medium so as to utilize limited volume of information content of the information recording medium effectively. The high degree compression technology is represented by not only data compression by correlation within one frame, which is a unit of video, but also a method of compressing data by correlation among a plurality of frames, which are adjacent to each other temporally. It is widely utilized for recording and transmitting video information.
In case of editing a result of data compression of video information, it is impossible to delete a frame by frame if a frame correlation is utilized. It is caused by that a frame to be referred can not be decoded if a referring frame to be correlated is deleted. Therefore, it is commonly prepared for a subsequent editing process that a plurality of frames are grouped in blocks and the blocks are encoded so as to be able to process them independently without processing frame correlation among the blocks. These block data, which are encoded block by block basis, are well known that each data volume varies by complexity of video signal in a block or a degree of correlation among frames.
Block data mentioned above are recorded on an information recording medium. However, it is necessary to be considered that a search operation can easily be performed in a reproduction process with arranging the block data in a sector from a head of the sector so as to occupy an integer number of sectors. It is realized by a well-known method that block data are encoded with including embedded data at an end of the block data. Accordingly, block data are recorded in an information region xe2x80x9cAxe2x80x9d as shown in FIG. 1.
It is commonly performed that a video information is grouped in blocks by an individual number of frames so as to compress the video information efficiently. In other words, it shall be considered that a displaying period of each block shown in FIG. 1 is different from each other by a frame period as a unit. In addition thereto, a volume of block data is different from each other as shown in FIG. 1 since compression ratio per block is different from each other.
In case that the above mentioned method is compared with other method such as linear pulse code modulation (PCM) which is not compressed and has a proportional relation between a elapsed time and a total volume of coded data, it is conceivable that a search reproduction starting reproduction from a block data array at a designated timing is very difficult by the above mentioned method.
To solve the above-mentioned problem, the Japanese Patent Laid-open Publication No. 9-23404/1997, which is titled as xe2x80x9cMedium Recording Method, Apparatus Therefore and Medium Reproduction Apparatusxe2x80x9d, discloses that a search reproduction is performed by using a collation table which is previously recorded as a collation table of time recording location. According to the medium recording method disclosed in the above mentioned Japanese Patent Laid-open Publication, video information as prescribed main information is encoded by the MPEG (Moving Picture Experts Group) system, which is an international standard of moving picture, and a plurality of GOPs (Group of Pictures), which is a unit of compression, are produced, then the produced plural GOPs are recorded on a recording medium. In case that the video information is divided by a predetermined time unit, a start address of data at each time unit is produced and recorded on a recording medium in conjunction with plural GOPs.
According to the medium recording method, a collation table of time recording location is composed of arrays of reproduction start address at each predetermined time unit. Encoded data are grouped in blocks by a compression unit, GOP. The recording method records information indicating a head portion of a GOP as a reproduction start address. The FIG. 1 shows an arrangement of data array as one concept.
The current method mentioned above functions properly for a search reproduction under a condition of not updating a block data array such that a block data array is recorded on a read-only medium. However, some problems may happen when the block data array is updated. In case that a block data array is recorded on a rewritable recording medium, contents of the block data array can be edited. For example, it is conceivable that a reproduction is skipped by a block data unit during a period of xe2x80x9csxe2x80x9d as shown in FIG. 2. Generally, it is not necessary to erase a block data to be skipped since information, which designates reproduction sections and reproduction sequence of the reproduction sections, is recorded on a recording medium as reproduction control data.
In case of skipping the block data xe2x80x9cDxe2x80x9d shown in FIG. 2, the reproduction period xe2x80x9csxe2x80x9d for two block data xe2x80x9cDxe2x80x9d becomes zero in the reproduction mode, that is, two block data xe2x80x9cDxe2x80x9d equivalent to the reproduction period xe2x80x9csxe2x80x9d are not reproduced and the reproduction is forwarded to the subsequent blocks after the block data xe2x80x9cDxe2x80x9d. In addition thereto, the reproduction start address 3 shall be deleted from the collation table of time recording location since the reproduction start address 3 designates the section to be skipped. Further, all reproduction start addresses after the reproduction start address 4 and subsequent reproduction start addresses must be updated so as to designate correct location since the period xe2x80x9csxe2x80x9d is independent of a period xe2x80x9cuxe2x80x9d. Accordingly, it is necessary to recalculate address information based upon a correlation between a capacity of blocks subsequently to the block xe2x80x9cDxe2x80x9d and a reproduction period, and an editing process is disposed to be very complicated.
Accordingly, an object of the present invention is to provide an information recording medium recorded with a collation table of time recording location, which is suitable for editing of assigning a sectional skip, in conjunction with encoded data. Another object of the present invention is to provide an editing apparatus, which can assure simple and high speed editing.
In order to achieve the above object, the present invention provides, according to an aspect thereof, an information recording medium which comprises a first recording region recorded with a plurality of block data continuing in time sequence, wherein the plurality of block data are compressed by an encoding system of varying an amount of codes per each block after temporally continuing information signals are divided into a plurality of blocks, and comprises a second recording region recorded with at least more than one collation table of time recording location, wherein the collation table of time recording location is composed of more than one collation data by every fixed time interval for reproducing an arbitrary block data out of the plurality of block data recorded in the first recording region and time compensating data.
According to the aspect of the present invention, there provided an information recording medium which is further characterized by that the collation data includes a block data location information of designating a block data out of the plurality of block data recorded in the first recording region, which is reproduced at a timing of each fixed time interval xe2x80x9cuxe2x80x9d after reproduction begins with a head of the first recording region, and characterized by that the collation table of time recording location is recorded with continuous reproduction sections by xe2x80x9cmxe2x80x9d in the second recording region in case of xe2x80x9cmxe2x80x9d continuous reproduction sections existing in the first recording region by editing, where xe2x80x9cmxe2x80x9d is a natural number, and characterized by that a nth collation data of each collation table of time recording location, where xe2x80x9cnxe2x80x9d is a natural number, is composed of a combination of a block data location information designating the block data of one of the xe2x80x9cmxe2x80x9d continuous reproduction sections, which is reproduced at a time of (nxc3x97u)xe2x88x92c, where xe2x80x9cuxe2x80x9d is the aforementioned fixed time interval and xe2x80x9ccxe2x80x9d is a period of time, elapsed after reproduction begins with a head block data of one continuous reproduction section in response to the collation data and a time difference information of time difference between a reproduction start time of the block data designated by the block data location information and the time of (nxc3x97u)xe2x88x92c, and characterized by that the time compensating data is data of compensating the time xe2x80x9ccxe2x80x9d, in case that the nth collation data is information of designating block data to be reproduced by the nth collation data at a time of (nxc3x97u)xe2x88x92c elapsed after the reproduction of the continuous reproduction section is started.
According to another aspect of the present invention, there provided an editing apparatus and method comprising readout means for reading out a collation table of time recording location from an information recording medium of rewritable, which is composed of a first recording region recorded with a plurality of block data continuing in time sequence, wherein the plurality of block data are compressed by an encoding system of varying an amount of codes per each block after temporally continuing information signals are divided into blocks by predetermined time unit, and composed of a second recording region recorded with at least more than one collation table of time recording location, wherein the collation table of time recording location includes more than one collation data by each fixed time interval for reproducing an arbitrary block data out of the plurality of block data in the first recording region and a first time compensating data. The editing apparatus further comprises memory means for temporarily storing the collation table of time recording location read out from the second recording region by the readout means, skipping period designating means for designating skipping period of skipping a part of continuous reproduction section of the block data recorded in the information recording medium, dividing means for dividing the collation table of time recording location read out from the memory means in response to the designated skipping period, deleting means for deleting collation data from the divided collation table of time recording location, wherein the collation data designates block data at a skipping period, calculating means for calculating a second time compensating data in response to the skipping period, writing back means for writing back to the memory means a collation table of time recording location newly composed of combining collation data succeeding the collation data deleted by the deleting means with the second time compensating data in conjunction with a collation table of time recording location composed of the first time compensating data and the collation data preceding the collation data deleted, and writing means for reading out a plurality of collation tables of time recording location written back to the memory means by the writing back means and for writing the plurality of collation tables of time recording location into the second recording region of the information recording medium.
Accordingly, the present invention provides a rewritable information recording medium. An information signal continuing in time sequence is divided into blocks by predetermined time unit. The rewritable information recording medium comprises a first recording region recorded with a plurality of block data in time sequence after the blocks have been compressed by an encoding system of which an amount of codes of each block varies and a second recording region which is recorded with more than one collation data per fixed time interval and at least more than one collation table of time recording location including a first time compensating data for reproducing an arbitrarily block data from the first recording region. In case that the rewritable information recording medium is edited so as to skip one section of a series of block data, the previously recorded collation table of time recording location is read out from the information recording medium and the collation data is divided into two sections by the dividing means so as to posses block data location information in each continuous reproduction section since the continuous reproduction section is divided into two sections.
Successively, collation data designating block data of assigned skipping period is deleted from a divided collation table of time recording location. Since it is necessary to add time compensating data newly for a group of collation data in response to a later continuous reproduction section located after a skipping period in time sequence, a duration of reproduction time of block data to be reproduced is calculated prior to block data designated by collation data at a head of a group of collation data in response to the later continuous reproduction section. A second time compensating data is calculated by the calculated duration of reproduction time. A new collation table of time recording location is composed by combining the second time compensating data with collation data after the deleted collation data, which is a group of collation data, in response to the later continuous reproduction section located after a skipping period in time sequence and is written in the second recording region of the information recording medium. Accordingly, the present invention assures that each collation data can accurately be acknowledged as information at a time elapsing from a head of a continuous reproduction section by reproducing by using the new collation table of time recording location.
Other object and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.